code: def num_prototypes(self):
      return self.prototype_vectors.size(0)
  
file_path: flair/flair/nn/decoder.py
imports: import logging
  from typing import List, Optional
  import torch
  import flair
  from flair.data import Dictionary, Sentence
  from flair.embeddings import Embeddings
  from flair.nn.distance import CosineDistance, EuclideanDistance, HyperbolicDistance, LogitCosineDistance, NegativeScaledDotProduct
  from flair.training_utils import store_embeddings
label_desc: Use image node_id 2 for calling the PrototypicalDecoder obj's underlying member method code with example usage: obj.num_prototypes() and returns: self